1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to merging cells in cognitive radio, and more particularly, to merging cells involving merging adjacent cells in cognitive radio, and thus efficiently utilizing resources.
2. Description of the Related Art
As the use of wireless communication technology is increasingly required in daily life, various forms of wireless communication technology are being rapidly developed.
In particular, there is a sharp increase of services using wireless technologies, such as mobile communication, wireless local area network (WLAN), digital broadcasting, satellite communication, radio frequency identification (RFID)/ubiquitous sensor network (USN) and wireless broadband (WiBro). The diversification and increased use of wireless communication services are dramatically increasing the demand for limited frequency resources, thereby making the frequency resources more valuable. In order to efficiently use such valuable frequency resources, advanced countries are developing relevant technologies and conducting activities to implement frequency policies based on the technologies.
One of the technologies for efficiently using frequency resources is cognitive radio. Cognitive radio can detect an idle frequency, which is assigned but not used, and efficiently share the idle frequency.
Specifically, cognitive radio is a technology that automatically finds an unused frequency for each area and time and enables intended communication while protecting licensed radio stations nearby. Cognitive radio finds idle portions of the spectrum, determines a frequency bandwidth, a power level and a modulation scheme suitable for the environment, and uses the idle portion of the spectrum. Therefore, the limited frequency resources can be more efficiently used. Since 2004, the Institute of Electrical and Electronics Engineers (IEEE) has been trying to standardize cognitive radio technology using a television frequency band.
Specifically, the IEEE is implementing IEEE 802.22 using an ultra-high frequency (UHF) (channels 14 to 51) band, which is a high-quality frequency band. With little power, IEEE 802.22 can reach far while avoiding interference with incumbent users of public channels. Therefore, it can remove shadow areas in homes or offices.
IEEE 802.22 has a bandwidth of 6 MHz in the UHF band and increases throughput by bonding channels up to a maximum of three channels when necessary. In a cognitive radio environment, many cells overlap one another, and a usable frequency is limited. Therefore, some cells short of frequency resources may have difficulty securing frequency resources, thereby failing to satisfy quality of service for real-time data.
According to a conventional method suggested to satisfy quality of service in the cognitive radio environment, a base station short of frequency resources borrows frequency resources from another base station abundant with frequency resources. However, if this conventional method is used in an apartment building which is a densely populated form of housing, since a plurality of cells overlap one another, usable frequency resources are sharply reduced. Therefore, it is difficult to secure frequency resources through channel expansion and efficiently use a frequency spectrum. Furthermore, since the base station, which lends its frequency resources, can arbitrarily withdraw the frequency resources, service may be halted.